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Trigger Requirements

This study assesses the impact of map field size on muon reconstruction algorithms at LVL2 EF in high-energy physics experiments. The text describes requirements, hardware setup, access times, and algorithm performance for efficient muon reconstruction. Specific considerations like field precision, memory allocation, and performance bottlenecks are highlighted, along with ongoing studies evaluating map granularity effects on reconstruction quality and timing.

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Trigger Requirements

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  1. Trigger Requirements LVL2 MS long list to acknowledge people who reacted on a very short notice EF MS first thoughts from Alessandro Di Mattia, Giovanni Siragusa, Sergio Grancagnolo, Andrea Ventura, Michela Biglietti, Diana Scannicchio John Baines, Dmitri Emelyianov, Iwona Grabowska-Bold, Alan Poppleton ID trigger / PESA LVL2 ID EF ID ID/Muon fitting in offline

  2. ID requirements Current map field size and access time OK for ID algorithms in HLT At LVL2 the access time is about 10% of the overall latency of the algorithm BUT they would not like to see this increase. Impact on performance of a similar size map, less symmetric and less granular in B-filed steps needs to be studied. Field / Pt precision: > hard to quote an absolute number > let’s put it in the other way: ID HLT needs the best resolution possible with a field map size acceptable

  3. EF Hardware baseline setup of EF: 8 core PCs, 1GByte memory per core (upgradable to 2) 1 processing task (EF process) running per core 1 GByte of memory available per process Recent Technical run: exercise the HLT sw on pre-series of the final hardware measured ~700 MBytes allocated by a single EF process (running EF for all slices: single muon/electron/gamma/tau/etc… trigger) using standard Athena Tools (i.e. magnetic field map and access tools) B-field of up to 100 MBytes (now 30MByte) are affordable and leave contingency for extra algorithms to be included in EF 1 GByte possible only on upgraded hardware (not foreseen at the moment)

  4. EF Muon Spectrometer TrigMoore uses –up to now- the offline iPatRecFitter (global Runge-Kutta based fit) Access to the field was optimized at some point on the available map: step in most of the MS volume is 320 mm, sometimes 160, 80, 40 mm (3 accesses per step to account for the local gradient) – the optimization was based on the process of using a very low step size as starting condition and increasing it up to un-observable pt measurement degradation (both on average value and resolution); Depending on the region, a given step is chosen;  Without re-optimizing the access to the map (the step size in each region) the size of the magnetic field map does not impact on the number of accesses but just for the time of a single access takes;  Field look-ups are probably the timing bottleneck for the fit !  MooMakeTracks (fit in TrigMoore based on iPatRec) takes more than 1/3 of the total TrigMoore time/event: 400ms for single muons in nominal background conditions at high luminosity) – 1s EF total latency

  5. From M.Biglietti and TrigMoore group talk at T&P week in May 2006: Muon EF performance

  6. EF Muon Spectrometer TrigMoore performance Long study to see the effect of a coarse grained map used in EF reconstruction for a detailed (nominal) map in simulation or for data ! The exercise just started with the following MS maps: • default map • 40gaus step for MS only • 80gaus step for MS only • 80gaus step + doubled step in phi and z (MS only) look at total timing of TrigMoore/track (not even isolating the fit !) • no observable effects look at measured pt for 6 GeV and 20 GeV single muons (integrating in eta/phi !) granularity in phi-eta of the performance study would be necessary  high statistics needed • no observable effects

  7. EF Muon Spectrometer

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